Drying cylinders

ABSTRACT

This invention relates to improvements in drying cylinders for papermaking machines which comprise two concentric cylindrical casings, the confronting walls of which provide a chamber which is separated into individual compartments each of which is fed with controlled quantities of steam, the cylinder also including an evacuation system for the condensed liquid.

United States Patent Strube Feh.22,1972

[54] DRYING EYLHNDERS [72] Inventor: Henri Robert Strube, Paris, France [73] Assignee: Societe de Recherches et de Realisations lndustrielles S.R.R.l. (Societe Anonyme), Paris, France [22] Filed: July 17, 1968 211 Appl. No.: 745,521

[52] U.S.Cl ..34/l24, 165/89 [51] Int. Cl ..F26b 11/02 [58] Field ofSearch ..34/122, 124; 165/89, 124

[56] References Cited UNITED STATES PATENTS Messinger 165/89 X Grierson 165/89 Messinger ..34/1 24 Ohlson et al...... ..34/124 Primary Examiner-Charles Sukalo Assistant Examiner-Theophil W. Streule Attorney-Edwin E. Greigg [5 7] ABSTRACT This invention relates to improvements in drying cylinders for papermaking machines which comprise two concentric cylindrical casings, the confronting walls of which provide a chamber which is separated into individual compartments each of which is fed with controlled quantities of steam, the cylinder also including an evacuation system for the condensed liquid. 7

7 Claims, 3 Drawing Figures DRYING CYLINDERS The present invention relates to improvements in papermaking machines wherein bands of moisture-bearing paper to be dried are passed continuously over a series of hollow rotary cylinders, into the interiors of which steam is introduced under pressure. With these drying cylinders, heat transfer is effected by conduction through the external wall of the casing of the cylinders, and the heat for evaporation of the moisture content of the paper causes condensation of the steam, the condensate being evacuated by an exhausting device.

More particularly, the invention is concerned with dried cylinders which comprise an internal cylindrical casing that extends concentric to or coaxial with an external cylindrical casing, the two spaced cylindrical walls defining an annular chamber within which rapid circulation of steam is effected.

Such dried cylinders, whether provided with annular chambers or not, do not allow the temperature to be controlled or varied at separate points on the same generatrix of the cylinders, i.e., in the direction of the width of the paper band to be dried. The moisture in a paper band to be dried varies in the transverse direction to such an extent that with presently known cylinders it is impossible to obtain a uniform degree of dryness of the paper traveling thereover.

In order to make the variations in dryness in the transverse direction of the paper strip less appreciable, the drying is normally carried out to a degree of dryness greater than that which would correspond to the optimum conditions for the ultimate utilization of the paper. When it is necessary to provide a paper product having a higher degree of moisture, which is more compatible with this utilization, and closer to uniformity in the transverse direction, it is necessary to have recourse to a conditioning apparatus separate from the papermaking machine and this necessitates a separate treatment which makes the final product considerably more expensive.

Attempts have been made to remedy these disadvantages by installing in the drier various elements for control of the blowing of air, and in particular of felt drier rollers for correcting the dryness as well as blower ramps the discharge of which is variable in a direction transverse of the cylinders or even by providing individual corrector hoods having wide mouth discharge areas.

Some of these apparatus, while bringing about an appreciable improvement in the transverse drying of the paper band as it travels over the cylinder, have nevertheless not entirely solved the problems which are known to increase as the machines attain greater size and speed.

SUMMARY OF THE INVENTION The present invention provides a drier cylinder for drying paper in paperrnaking machines comprising two coaxial cylindrical casings defining therebetween an annular chamber for the circulation of steam, the chamber being divided along its length into a plurality of adjacent compartments which are respective connected to a group of suction conduits for evacuating condensed liquid and to a group of feeding conduits. A rotary distributor is provided comprising a fixed outer member and an inner member coaxially mounted on the cylinder, the members defining annular connecting chambers which are connected to the conduits and to valves for controlling the rate of flow through the conduits.

The external surface of the cylinder through which heat exchange is effected with the moist paper band or web is thus subdivided into as many longitudinally aligned annular zones as there are compartments, in each of which it is sufficient to modify, if such is required, the quantity and, consequently, the pressure and the temperature of the steam admitted and therefore the amount of heat transferred in order to thus vary in a very precise and controlled manner the degree of drying. Thus, it becomes possible to correct inequalities in the degree of moisture in the transverse direction of the band to be dried, the causes of which are often variable between the time of the discharge of the pulp from the distributor tank to its arrival at the drier and also during its passage thereover, and to achieve a transverse drying which is practically uniform.

The supply to each annular compartment can be controlled by means of a distribution valve in the corresponding supply ducting either in the interior of the cylinder, or outside the latter with the interpositioning of a rotary housing having a plurality of passages.

Each distribution valve may be advantageously provided with a device for controlling the dryness of the corresponding elementary band of the paper being dried.

Continuous automatic regulation of the transverse dryness of the paper band is thus achieved with considerably more efficiency than heretofore known by employing a relatively smaller number of drying cylinders. These may be substituted for the final drier cylinders without modification of the drier.

It is also an object of the invention to improve the exhausting devices of the different compartments in order to improve the general functioning of the drier cylinder.

The invention will be better understood, and additional objects and advantages will become more apparent, from a reading of the following detailed specification taken in conjunction with the drawings, in which:

FIG. lla shows a schematic view in axial cross section of a drier cylinder with a rotary housing having a plurality of passages shown in FIG. lb;

FIG. 2 shows a view in transverse section along line II-II of FIG. la; and

FIG. 3 shows a partial broken-away view in transverse section through a modified drier cylinder for use in machines which operate at high speed.

- In the drawing, S indicates a drier cylinder formed of two coaxial cylindrical casings P1 and P2 defining an annular chamber connected by radially extending arms B affixed to tubular hubs M1 and M2 and subdivided by partitions a1, a2, a3 and 1 a4 into a plurality of adjacent annular compartments or chambers all, c2, c3, c4 and c5.

Into each of these compartments open at closely spaced positions there extends a steam supply duct Vll, V2, V3, V4 and V5 and a condensate evacuation duct E1, E2, E3, E4 and E5 having an exhaustion device and a check valve, and of the latter only one is shown at p3 on the drawing. For the sake of simplicity, these ducts, with the exceptions of the ducts V3 and E3, have been shown schematically.

The stem ducts, on the one hand, and the condensate evacuation ducts, on the other hand, are disposed at equal annular spacings about the wall of the cylinder so as to provide balance thereof. The stem ducts are connected to ducts bll, b2, b3, b4 and b5 extending parallel to the axis of the cylinder and adjacent thereto, whereas the condensate evacuation ducts discharge into a return collector C. The ducts bll, b2, b3, b4 and b5 are connected to a rotary distribution housing W, carried by the hub Mll, represented diagrammatically in FIG. lb, and in which the collector C terminates.

This rotary distribution housing W comprises a rotor L fixed for rotation with the hub M1 of the cylinder S and is provided with five annular chambers i1, i2, i3, i4 and 15 which are separated from one another by means of the seals shown and into which discharge the ducts V1, V2, V3, V4 and V5 shown in FIG. la, the rotor L also having a sixth annular chamber i6 into which the collector C discharges the condensed liquids which are to be evacuated.

Fixed ducts depicted at U1, U2, U3, U4 and US, which are connected to a common steam source (not shown) and provided with valves R1, R2, R3, R4 and R5, discharge into the annular chambers i1, i2, i3, i4 and 15.

It is also possible as an alternative to dispose the valves in the interior of the cylinder, as shown in broken lines at R3 in FIGS. 2 and 3. It is also contemplated that they may be controlled manually when stationary or they may be remotely controlled where desirable.

In both instances described the steam output into the compartments can be controlled by various devices (not shown) for registering the moisture profile disposed at the end of the machine. The moisture content is sensed in strips of the paper corresponding to the size of the compartments, and an integrator in the registering device transmits, for each strip, a

signal whose intensity controls the steam discharge into the corresponding compartment.

There is indicated at F the direction of rotation of the cylinder, while the single arrows indicate the paths of the steam and the double arrows indicate the paths of the condensed water.

In each compartment there is disposed substantially in line with the evacuation duct a closure baffle (of which one is best shown at d3 in FIG. 2) which extends tangentially to the evacuation duct, i.e., inclined from upstream to downstream in the centrifuge direction. This baffle causes a forced discharge of the condensed water as indicated by the double arrow shown in FIG. 2.

In another embodiment, in accordance with this concept, of a machine operating at high speed in which the ring of condensed water forms more rapidly than in a conventional drier cylinder because the closure baffle discharges it at the same speed as the periphery of the cylinder against which it cannot slide, a deflector e3 has been provided (F l0. 3). Adjoining the inner casing and the two lateral faces of its compartment, the deflector is inclined in a direction opposite to the closure baffle and leaves at its outer edge a free space of l or 2 millimeters which ensures siphoning of the condensed water by lowering the pressure between the annular compartment and the discharge collector, and by reducing the thickness of the ring of water to about 1 or 2 millimeters.

That which is claimed is:

1. In a rotatable dryer cylinder for the drying ofpaper in papermaking machines, the combination comprising, coaxial inner and outer cylinder walls defining an annular chamber there between for the circulation of vapor, said chamber having annular means subdividing the chamber along its length dimension into a plurality of juxtaposed separate compartments, at least one apertured end closure means for the cylinder, a rotary distributor having a fixed outer member and a concentrically disposed rotatable inner member associated with at least one of said apertured end closure means, said concentric inner and outer members having defined therebetween a series of separate annular chambers, inlet and outlet means connected to said chambers, control means for feeding stem to said annular chambers of said rotary distributor, and therethrough to said juxtaposed separate compartment in said dryer cylinder, said outlet means exhausting condensate from said separate compartments axially of said rotary distributor through a collector means to one of said annular chambers in said rotary distributor.

2. A drier cylinder according to claim 1, wherein the control means comprise valve means disposed in the inlet means in the cylinder.

3. The drier cylinder according to claim 1, wherein the con trol means for the inlet means is arranged to vary the degree of heat transmitted to the respective compartments.

4. A drier cylinder according to claim I, wherein each compartment is provided with tangentially disposed baffle means.

5. A drier cylinder according to claim 4, wherein said baffle means in said compartments are arranged to converge toward the outer wall of said cylinder.

6. A drier cylinder according to claim 4, wherein at least one of said baffles means has a shorter radially extending length dimension than an adjacent baffle means.

7. A dryer cylinder according to claim 1, in which each of said inlet means is associated with a corresponding connecting chamber and said flow control means. 

1. In a rotatable dryer cylinder for the drying of paper in papermaking machines, the combination comprising, coaxial inner and outer cylinder walls defining an annular chamber there between for the circulation of vapor, said chamber having annular means subdividing the chamber along its length dimension into a plurality of juxtaposed separate compartments, at least one apertured end closure means for the cylinder, a rotary distributor having a fixed outer member and a concentrically disposed rotatable inner member associated with at least one of said apertured end closure means, said concentric inner and outer members having defined therebetween a series of separate annular chambers, inlet and outlet means connected to said chambers, control means for feeding stem to said annular chambers of said rotary distributor, and therethrough to said juxtaposed separate compartment in said dryer cylinder, said outlet means exhausting condEnsate from said separate compartments axially of said rotary distributor through a collector means to one of said annular chambers in said rotary distributor.
 2. A drier cylinder according to claim 1, wherein the control means comprise valve means disposed in the inlet means in the cylinder.
 3. The drier cylinder according to claim 1, wherein the control means for the inlet means is arranged to vary the degree of heat transmitted to the respective compartments.
 4. A drier cylinder according to claim 1, wherein each compartment is provided with tangentially disposed baffle means.
 5. A drier cylinder according to claim 4, wherein said baffle means in said compartments are arranged to converge toward the outer wall of said cylinder.
 6. A drier cylinder according to claim 4, wherein at least one of said baffles means has a shorter radially extending length dimension than an adjacent baffle means.
 7. A dryer cylinder according to claim 1, in which each of said inlet means is associated with a corresponding connecting chamber and said flow control means. 